How Do Soil Moisture Meters Work Without Batteries?

If your soil meter hasn’t moved an inch since you put it in the pot, you might have looked for a place to add new batteries, assuming it was powerless. If you were surprised to find there’s no space for a battery, not even a watch battery, you might be wondering how the moisture meter had worked all this time. How do soil moisture meters work without batteries? 

Soil moisture meters can work without batteries because, by design, they are batteries. They utilize two different metals and an electrolyte (the moisture within the pot) to give you a reading on the moisture in your plant. This is also why they don’t read anything if they sit out on the counter. 

Of course, some soil meters take batteries or are solar-powered, but for this article, I’ll go over the ins and out’s of two-pronged, battery-free soil moisture meters. I’ll explain how your meter works as a self-powering battery to indicate the moisture levels of your plants and how to use your moisture meter to get the best reading. 

Do I Need Batteries for My Soil Moisture Meter?

Some moisture meters take batteries, and the battery box will be pretty straightforward. But for those that don’t, you might be wondering how it even works. Moisture meters accurately depict whether your plant needed more or less water, but how does it work with any electrical power? 

You don’t need batteries for a soil moisture meter because it is the battery. Moisture meters harness energy by using the moisture within your soil to conduct power, as well as the two metals on the meter. 

This is why tons of moisture will shoot the arrow up to the “moist” setting, and low moisture will weakly move the meter to the “dry.” Because the soil moisture meter acts like a battery with moisture as its power, it won’t move when there is no moisture to power it. 

So, if you’re looking at your soil moisture meter wondering where to put in the new batteries, as it stays unmoving, then it’s likely that you have a very dry plant on your hands. Below, we help further explain this concept with a battery crash course. 

A Crash Course in Batteries

In the simplest of explanations, Batteries use two conducting metals and an electrolyte to power things. Battery acid is the common electrolyte, and ion liquids from lithium batteries can be found in your phone. Try to picture the batteries in your remote or your alarm clock. The metal end of the battery connects to another metal spring in the remote or clock, with the battery acid (which is heavily coated in the battery to protect us) acting as an electrolyte in the middle. 

This TedEd video is less than five minutes and gives some helpful insights into how batteries work: 

Electricity conduction has a long and thorough history, which is why we’re now able to power cars with electricity and hook up all our houses to a system of circuit boards. Batteries can seem like a complicated subject, but for this article, all you need to know is that at a very micro level, batteries consist of two metals and an electrolyte. 

Let’s discuss how this simple formula turns your soil moisture meter into a battery. 

Soil Moisture Meters Are Batteries 

Our battery crash course taught us that two kinds of metal and an electrolyte are needed to make a battery and harness electrical energy or power. When observing your soil moisture meter, you’ll notice it already has two different kinds of metals on it that both penetrate the soil. Then, the moisture within your plants will power up the meter, acting as the electrolyte. 

Soil that’s high in moisture will send the meter all the way to 10 quickly. However, soil with less moisture will make the meter move more slowly. This is because the moisture, as an electrolyte, additionally supports the meter in its power. Lots of water will make a stronger (yet still, very weak) battery, and little water will make the battery less intense. This is also why you shouldn’t have your moisture meter always in your plant, as watering might confuse the moisture meter. 

If you’re worried your meter is broken or needs batteries because no movement has occurred, then it’s likely that your soil (or the area you’re penetrating) is arid, or that you’re not sticking both pieces of metal in all the way. You can test out your soil meter outside if this is your worry. 

The Bottom Line: Your Soil Moisture Meter Works Without Batteries

Your soil moisture meter works without batteries because, by engineering properties, your soil moisture meter is a battery. Your meter uses two different metals and an electrolyte (i.e., the moisture in the soil) to produce small amounts of power and give you a reading. 

The power will be more substantial if you have a more significant amount of the electrolyte (water), indicating a very moist plant. The battery will be weak if there is no moisture and indicates a dry plant. 

How To Use a Soil Moisture Meter

If the news that your soil moisture meter is a battery is new to you, then you might be wondering if you’re even using the thing correctly. Fortunately, it’s pretty straightforward, and little can go wrong along the way. 

Here’s how to use a moisture meter:

  1. Set the meter to the “moisture” setting (or whatever setting you’re trying to read).
  2. Stick the two metal prongs two-thirds of the way down into your plant pot.
  3. Wait about one minute, then check for a reading.

It’s essential that you stick your moisture meter down into the dirt, as the top layer may be hoarding some water and give you an inaccurate reading. Additionally, if you stick your meter too far down into the dirt, it may give you a dryer reading. This won’t accurately represent what your plant roots are utilizing, as it’s too far down. 

As long as both sticks touch the soil, your moisture meter should work just fine. 

What a Soil Moisture Meter Can Detect

Moisture meters are incredible for, as you guessed, reading the amount of moisture within your plant’s soil

If you’re having trouble getting an accurate reading, then there’s a chance you have your moisture meter in the wrong setting. While most meters will only indicate the moisture of your plant, there are some fancier ones out there that will also indicate: 

  • Moisture 
  • Light  
  • pH (acidity in your soil)  

What a Soil Moisture Meter Won’t Tell You 

If you determine your meter just isn’t measuring your soil accurately, then it could be a meter problem. It’s rare, but your moisture meter may become uncalibrated. This can mean an inaccurate reading for water, light, and pH ratings. 

The moisture meter will indicate how much moisture is in the soil of your plants, but it won’t tell you if it’s enough or too much for the plant you’re watering. Some moisture meters will come with a handbook, which will tell you the optimal moisture levels for different plants. One of your plants can be a three on the meter optimally, while another may need to be a nine. But treating all your plants like they need the same moisture level will be unbeneficial for their growth. 

Additionally, if your moisture meter tells you your plants are watered enough, but they’re still dying, it could have something to do with water quality. All water has a pH, and if your tap water is too high or too low, it can affect your plants. The pH meter can be helpful with this because it tests the acidity of your soil. Again, some books and guides should indicate the optimal level of acidity in your soil per plant. Not all plants need the same thing. 

Your moisture meter also won’t tell you if there’s something more nefarious happening in your plants, such as an infection or an infestation. If you seem to be doing everything right, and your plants aren’t doing well, you should look for other signs of illness or rot. 


Soil moisture meters work without batteries because they are, themselves, batteries. A basic battery is comprised of: 

  • Two pieces of metal 
  • An electrolyte 

If it works without batteries, then your soil moisture meter likely has two different prongs of metal or one prong of metal with two types of metal on it. The moisture within your soil will act as an electrolyte, powering up the meter to let you know how much moisture your plants are getting. 

Though moisture is huge, it’s not the only indicator of a healthy plant. Make sure to check for pH, light, and rot, too.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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